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Losambe, Alengo Nicole

Nutritional and Food Sciences

2008

M.S.

Currently, the literature contains very little information relating to the microbiological characteristics of commercial Cream cheese. Furthermore, little is known about the potential for microbial-induced syneresis in commercial Cream cheese. The objective of this first study was to evaluate microbiological characteristics of commercial Cream cheese samples during refrigerated storage and under temperature abuse conditions. Retail samples of Cream cheese representing three different brands were obtained from local sources. Three retail samples of each brand, each with a different expiration date, were obtained and stored at 4°C. Split samples were evaluated for aerobic plate count (APC) and aerobic spore count (ASC) immediately upon receipt (>-60 d before expiration) and again on the expiration date printed on the package. Also, split samples were subjected to temperature abuse at 20°C for 14 d and then enumerated for APC and ASC. Effects of storage time (at receipt v. at expiration) and temperature abuse on microbial counts were evaluated ANOVA using a repeated measures design. Upon receipt, all 3 brands of Cream cheese had very low APC values (1.70±1.56 log CFU/g) which did not differ significantly among the 3 brands. Similarly, initial ASC values were also very low (1.50±1.47 CFU/g) and did not differ among brands. APC and ASC values at the expiration date did not differ significantly from their initial values, indicating little or no microbial growth during storage at 4°C for>60 d. Similarly, APC and ASC values after temperature abuse at 20°C for 14 d did not differ significantly from the initial values. None of the samples displayed any visible syneresis at the expiration date or after temperature abuse. In summary, all of the samples resisted syneresis and had very low microbial counts, comprised mostly of aerobic spore formers, which remained low throughout product shelf life and during temperature abuse.
The objective of the second study was to evaluate the water-holding capacity and microbiological characteristics of commercial Cream cheese, Cream cheese spread and Neufchatel cheese samples before and after temperature abuse. Three retail samples of Cream cheese, Cream cheese spread and Neufchatel cheese representing 3 different brands were obtained from local supermarkets. All samples had>-60 d remaining before expiration. Split samples were stored at 20°C for 14 d and evaluated before and after storage for aerobic plate count (APC), aerobic spore count (ASC), and expressible serum (ES), obtained by centrifugation at 12,500 x g for 75 min at 25°C. Typical colonies were picked from APC and ASC and identified using the RiboPrinterB system. Effects of cheese type (Cream cheese v. Cream cheese spread v. Neufchatel cheese) and temperature abuse on ES and microbial counts were evaluated by ANOVA using a repeated measures design. Upon receipt, Cream cheese, Cream cheese spread and Neufchatel cheese samples had very low APC (1.80±1.49, 1.66±.32,2.7±.40 log CFU/g) and ASC (1.53±1.0, 1.43±0.9,2.3±.20 log CFU/g) values, which did differ significantly. APC, ASC and ES values after temperature abuse did not differ significantly. Colonies picked from APC and ASC were identified as Bacilluspumilus, Bacillus cereus, Bacillus subtilis and Bacillus lichenformans. In summary, all of the samples had very low microbial counts, comprised mostly of aerobic spore formers, which remained low despite temperature abuse. Temperature abuse did not cause a loss of water-holding capacity in these microbiologically stable samples.